From: Zach Brown <zab@zabbo.net>
To: "Ted Ts'o" <tytso@mit.edu>,
Yongqiang Yang <xiaoqiangnk@gmail.com>,
Phillip Susi <phillsusi@gmail.com>,
Andreas Dilger <adilger@whamcloud.com>,
Lukas Czerner <lczerner@redhat.com>,
Jacek Luczak <difrost.kernel@gmail.com>,
"linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>
Subject: Re: getdents - ext4 vs btrfs performance
Date: Wed, 14 Mar 2012 10:17:37 -0400 [thread overview]
Message-ID: <4F60A881.3070607@zabbo.net> (raw)
In-Reply-To: <20120314025108.GF15379@thunk.org>
> We could do this if we have two b-trees, one indexed by filename and
> one indexed by inode number, which is what JFS (and I believe btrfs)
> does.
Typically the inode number of the destination inode isn't used to index
entries for a readdir tree because of (wait for it) hard links. You end
up right back where you started with multiple entries per key.
A painful solution is to have the key in the readdir tree allocated by
the tree itself -- count key populations in subtrees per child pointer
and use that to find free keys. You still have the problem of
correlating entry keys and the location of inodes, but at least now you
have a structure to navigate to try and do that. You can also trivially
re-use freed keys and have densely packed readdir keys that won't break
32bit f_pos so quickly.
btrfs just punts and has an incrementing 64bit counter per directory
that determines a new entry's position in readdir. Accompanied by the
obligatory "will be smarter some day" comment :).
- z
next prev parent reply other threads:[~2012-03-14 14:17 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-29 13:52 getdents - ext4 vs btrfs performance Jacek Luczak
2012-02-29 13:55 ` Jacek Luczak
2012-02-29 14:07 ` Jacek Luczak
2012-02-29 14:21 ` Jacek Luczak
2012-02-29 14:42 ` Chris Mason
2012-02-29 14:55 ` Jacek Luczak
2012-03-01 13:35 ` Jacek Luczak
2012-03-01 13:50 ` Hillf Danton
2012-03-01 14:03 ` Jacek Luczak
2012-03-01 14:18 ` Chris Mason
2012-03-01 14:43 ` Jacek Luczak
2012-03-01 14:51 ` Chris Mason
2012-03-01 14:57 ` Jacek Luczak
2012-03-01 18:42 ` Ted Ts'o
2012-03-02 9:51 ` Jacek Luczak
2012-03-01 4:44 ` Theodore Tso
2012-03-01 14:38 ` Chris Mason
2012-03-02 10:05 ` Jacek Luczak
2012-03-02 14:00 ` Chris Mason
2012-03-02 14:16 ` Jacek Luczak
2012-03-02 14:26 ` Chris Mason
2012-03-02 19:32 ` Ted Ts'o
2012-03-02 19:50 ` Chris Mason
2012-03-05 13:10 ` Jan Kara
2012-03-03 22:41 ` Jacek Luczak
2012-03-04 10:25 ` Jacek Luczak
2012-03-05 11:32 ` Jacek Luczak
2012-03-06 0:37 ` Chris Mason
2012-03-08 17:02 ` Phillip Susi
2012-03-09 11:29 ` Lukas Czerner
2012-03-09 14:34 ` Chris Mason
2012-03-10 0:09 ` Andreas Dilger
2012-03-10 4:48 ` Ted Ts'o
2012-03-11 10:30 ` Andreas Dilger
2012-03-11 16:13 ` Ted Ts'o
2012-03-15 10:42 ` Jacek Luczak
2012-03-18 20:56 ` Ted Ts'o
2012-03-13 19:05 ` Phillip Susi
2012-03-13 19:53 ` Ted Ts'o
2012-03-13 20:22 ` Phillip Susi
2012-03-13 21:33 ` Ted Ts'o
2012-03-14 2:48 ` Yongqiang Yang
2012-03-14 2:51 ` Ted Ts'o
2012-03-14 14:17 ` Zach Brown [this message]
2012-03-14 16:48 ` Ted Ts'o
2012-03-14 17:37 ` Zach Brown
2012-03-14 8:12 ` Lukas Czerner
2012-03-14 9:29 ` Yongqiang Yang
2012-03-14 9:38 ` Lukas Czerner
2012-03-14 12:50 ` Ted Ts'o
2012-03-14 14:34 ` Lukas Czerner
2012-03-14 17:02 ` Ted Ts'o
2012-03-14 19:17 ` Chris Mason
2012-03-14 14:28 ` Phillip Susi
2012-03-14 16:54 ` Ted Ts'o
2012-03-10 3:52 ` Ted Ts'o
2012-03-15 7:59 ` Jacek Luczak
-- strict thread matches above, loose matches on Subject: below --
2012-02-29 13:31 Jacek Luczak
2012-02-29 13:51 ` Chris Mason
2012-02-29 14:00 ` Lukas Czerner
2012-02-29 14:05 ` Chris Mason
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